|
Post by joanlluch on Apr 8, 2015 13:06:40 GMT
I just wanted to bring this up. I think it's a pity this tread going lost under many others as it has happened over the last week. I hope Michael cold have gotten better -or fully disappeared- after such a while. :-)
What about (some more) practical or theoretical design tips for steam locomotive Performance and Efficiency? Can it all be ultimately related to steam pressure and superheat temperature?
|
|
|
Post by Deleted on Apr 8, 2015 13:23:31 GMT
Hi Joan ,
Much better now . Answering questions on this thread needs a clear head - which I certainly didn't have last week .
Thanks ,
MichaelW
|
|
|
Post by miketaylor on Apr 8, 2015 13:54:23 GMT
Hi Michaelw,
Glad you are feeling better.
I had intended ot bring this thread back to the top but Joan beat me to it. We were in danger of hijacking Andy's scale galloping horseman which was really addressing rather different aspects of scale.
I have previously noted that i am designing a freelance Garrett. This introduces various aspects of steam distribution which are, I think, more important than with a conventional loco.
The HP steam runs from boiler to cylinders are relatively long and I am not clear to what extent this influences things. Obviously lagging of the pipe runs is likely to be important but I am also unclear of the requirements for pipe diameter - both HP and exhaust steam.
You commented on choked steam runs - but then went on to comment about running with the regulator nearly shut for most of the time which seems to imply somewhat the opposite problem??
You also commented on cooling of superheated steam - I would have thought this need not be a big problem on a normal arrangement with the cylinders right next to the smokebox, but that it is one which I am likely to encounter.
Mike
|
|
|
Post by Deleted on Apr 12, 2015 22:19:31 GMT
Hi Mike ,
Sorry not to have answered your questions and those of others .
I have been greatly discouraged from pursuing this thread by the usual donkeys that have made it very clear to me that they think that there is no place on this forum for any kind of technical discussion . Basically in their view steam engines should be built strictly to the words of LBSC , they cannot possibly be bettered and what the hell does an armchair engineer like me I know about anything anyway .
And I've heard it all before from another lot of donkeys on the ME forum .
MichaelW
|
|
|
Post by simplyloco on Apr 12, 2015 22:30:54 GMT
Please don't be too discouraged Michael, as I, and perhaps others on here, don't know any better than to follow the words and music. When I was in the Army I studied the theory and practice of steam as applied to power generation: I even got the maths right when it came to understanding and sizing injectors, but to understand what goes on in those little cylinders so far removed from the power house is beyond me, and I prefer to remain in the comfort zone so ably provided by LBSC. John
|
|
jma1009
Elder Statesman
Posts: 5,901
|
Post by jma1009 on Apr 12, 2015 22:39:21 GMT
hi michael,
whether the 'mainstream' agree with you or i or anyone else isnt really the issue, and one cannot expect 'everyone' to agree on the forum! by way of example, i know very well that my injectors work 100% and none of my locos have axlepumps fitted or hand pumps - but can i persuade everyone on the forum that this is the way to 'do things'?!!
however surely by promoting what im hinting at, the 'trickle down' effect is worth while and putting up with those who obviously have closed minds and wont agree to anything!!
please dont be discouraged! a lot of kicking and battering at a wall is required before it falls down and everyone sees the light!
cheers, julian
|
|
|
Post by miketaylor on Apr 13, 2015 6:14:36 GMT
Hi Michael,
Have to disagree with you rather.
Looking at this and other threads I would have said the "donkeys" are no more than a small minority at most.
I don't really see anyone who thinks LBSC is an infallible genius.
You won't find anyone who disagrees with Don Ashton's criticisms, and improvements, on LBSC valve gears for example. You'll find plenty who admit to having problems with them though.
I think JB has it pretty much right when he points out that for many people, LBSC is the clearest,simplest and most readily available resource when it comes to outlining a design and then putting it all together. People use him because his stuff is there and it generally works, the fact that it often doesn't work as well as it might is not always obvious.
Don't be discouraged: a lot of people are interested in what really makes the wheels go round and do actually want to make better locos.
(Also, I want to know your views on my steam problems!!!)
Mike
|
|
|
Post by runner42 on Apr 13, 2015 22:59:03 GMT
hi michael, i know very well that my injectors work 100% and none of my locos have axlepumps fitted or hand pumps - but can i persuade everyone on the forum that this is the way to 'do things'?!! cheers, julian Hi Julian,
your approach to having only one feedwater system is predicated on your ability to construct and your confidence in the injectors that you fit to your steam locomotives. In addition the ability to adjust feedwater and steam under running conditions. Not all of us can have the same ability and assurance as yourself. Us down under guys are required to comply with the AMBSC Code Part 1 requirements which specifies that there is at least two independent means of providing feedwater.
Hi Michael,
LBSC didn't provide a great deal of technical or engineering rationale for his designs, he approach was here it is take it or leave it. Most recipients accepted that approach, not interested in why or how it operated just happy that the end result worked in a reasonable fashion. ME's today require a better understanding of the design principles that where developed and understood by a select few in days gone by. I hope this thread will provide the insight that many are seeking.
Brian
|
|
jma1009
Elder Statesman
Posts: 5,901
|
Post by jma1009 on Apr 13, 2015 23:11:38 GMT
hi brian,
i completely agree with you. i think that on smaller 3.5"g locos problems arise, but on a loco your size no problem should arise! can i tempt you to have 'a go' at making your own injectors?! (just dont follow the LBSC designs or descriptions for making same!)
LBSC was a 2.5"g loco builder essentially. hence the use of handpumps and axlepumps. plus he never had to deal with the problems of running on a long continuous track passenger hauling - his famous 'polar route' being actually relatively short and he didnt do passenger hauling. if his locos could pull him round his own track at Purley without passengers he was quite happy!
cheers, julian
|
|
|
Post by Jim Woods on Apr 14, 2015 1:41:53 GMT
Hi Guys,
I would like to stick up for LBSC and the time he was designing. To compare his designs to what is being done today is like comparing a model A Ford to the latest Range Rover. When he started out most 2 1/2 loco's had a meths fired "smithies" boiler that couldn't pull the skin off a rice pudding. With LBSC and a couple of others fiddling around in their workshops they got them to burn coal and haul real people. If you look at the evolution of LBSC designs over the time he was writing, you can see a huge leap forward and laid the platform for others to take on the way forward. so really, we should have loco's that are vastly better today than in the 1920's or 1950's. I have 3 LBSC designed loco's and one (P.V.Baker)was built in 1952 and still does a good days haulage because the design was good and it's builder was skilled enough to reproduce what LBSC intended. It almost won the NZ version of IMLEC back in the 80's. a beautiful 2 1/2 Fayette did win the NZ trials in the late 70's. I believe that what LBSC did was to design and build himself, something a novice model engineer with a treadle lathe, few files and a drill could build and make go. To each their own, that what I think makes model engineering a great thing.
The Isle of Man Loco I built is a much better design, but that was done in the 1980's and I used modern and traditional methods to build it 15 years ago. It is a better loco than my first one which is a Simplex, It still goes well even though it is nearly worn out. she has at least 3/16 of lost motion at the valve rod.
Hind sight is a wonderful thing. What do we see looking forward? ceramic's for the cylinders? that would be interesting.
My tuppence worth :-)
Jim
|
|
|
Post by Deleted on Apr 14, 2015 15:44:20 GMT
QED
|
|
|
Post by chris vine on Apr 14, 2015 16:56:26 GMT
Hi Michael,
I have been enjoying what you write about the engineering of locos.
If by "QED" you mean that the support for LBSC (in the above post) means your information is falling on stony ground, then I think you are wrong in that. I think Jim was just supporting what LBSC did in his own time.
I would like to add that my understanding of the principles of engineering originally came from reading Model Engineer. The fact that I am a chartered mechanical engineer is largely as a result of an in-built interest, but fed by ME etc. I think the beauty of the models at exhibitions and at the science museum was also a big factor in encouraging/inspiring me.
Of course, there might be precious little thermodynamics in a beautifully made model engine, even if it works, but they still inspire/delight me today.
so I, for one, am interested in this thread so please don't be put off - especially as I am sure Jim did not mean to put you off!!! There are a lot of avenues still to explore to improve the efficiency of our models. (if we normally reach 1 % then there is still 99% to go for...)
Chris.
|
|
|
Post by Jim Woods on Apr 14, 2015 20:50:17 GMT
yes, keep going Michael, sorry if I put you off.
I was talking about the evolution of our loco's. When I started out as an apprentice tool maker,32 years ago, all the stuff we did was segmented inserts. Now with CNC, wire cutting and spark erosion EDM machining, the whole game has changed. We can build bigger and better tooling today, faster with such a huge range of different materials. Like the slide valves/piston valves on my loco's are now aluminium bronze which we used on tooling to fold repainted sheet steel for a dishwasher outer wrapper without scratching. Ali-bronze is hard and slippery and has good wearing in a sliding motion, some grades are not so good in a rotary situation. I use P20+Si tool steel for the coupling rods because is very stable while machining and can resist rust. we use it for plastic injection tooling because it retains a high polish. I now do most design work by CAD and feed NC code to my mill. the modern idea now is to rough out the tooling to within say 0.25mm harden it then finish machine with a high speed (40,000+ rpm) mill using amazing carbide endmills. So I guess I look at the evolution of my trade in the short time I have been involved but seen where it came from. Where it is going too, who knows, but what a journey so far, and so be it for our wee loco's
Jim
|
|
jma1009
Elder Statesman
Posts: 5,901
|
Post by jma1009 on Apr 14, 2015 21:03:26 GMT
hi jim,
that is very interesting re ali bronze - i wasnt aware of that!
when i was an impecunious teenager i was given a manganeze bronze propellor to melt down into cast sticks for use as bearing material and other stuff from patterns i made as i couldnt afford to buy phos bronze or all the gunmetal castings i needed for my first loco. the manganese bronze must have been good and cast well as those coupling and conn rod bearings havent needed replacing - yet! it was just a pity to reduce most of it to swarf for the bearings!
cheers, julian
|
|
|
Post by Deleted on Apr 14, 2015 21:19:01 GMT
This thread was originally intended to be about design in abstract but it turned out that most people were more interested in the design and underlying theory of steam engines in particular .
So perhaps we could all of us start to explore the complex and fascinating subject of how a steam engine actually works .
MichaelW
|
|
|
Post by Deleted on Apr 14, 2015 21:59:27 GMT
(1) Just a quick note about water :
As far as anyone knows water can exist in four definate states and one possible theoretically predicted state .
The three common ones are in order of increasing temperature : ice , liquid water and steam .
There is also plasma which certainly exists at extreme high temperature and a maybe further state right down near absolute zero . These two are only of academic interest to us .
Water has the quite remarkable property that it is chemically stable over an enormous range of practical temperatures . Hard frozen ice , liquid water and steam at high superheat are chemically all exactly the same . This means that in steam applications water can be pumped to pressure , boiled to vapour , superheated , expanded and condensed over and over again without any degredation .
Water also has the essential property that chemically it only reacts very weakly with any materials likely to be used in a steam engine .
|
|
jma1009
Elder Statesman
Posts: 5,901
|
Post by jma1009 on Apr 14, 2015 22:05:05 GMT
hi michael,
many apologies for going off topic above.
please do continue as everything you post is quite fascinating and educational!
cheers, julian
|
|
|
Post by Deleted on Apr 14, 2015 22:21:34 GMT
hi michael, many apologies for going off topic above. please do continue as everything you post is quite fascinating and educational! cheers, julian Hi Julian , No apology needed at all . There are no off topic topics on this thread ! If anything interesting occurs to anybody that is even loosely relevant then please mention it . MichaelW
|
|
jma1009
Elder Statesman
Posts: 5,901
|
Post by jma1009 on Apr 14, 2015 22:38:48 GMT
thank you michael,
to get down to basics, and the nitty gritty, can i please mention superheaters?
i am not (as is well known) a fan of coaxial superheaters, and have fitted stainless radiant superheaters to Stepney (untried as yet) and LINDA (tried and tested) last weekend.
my general policy is determined by my 5"g GWR 0-6-0 loco which has 3 x 1" OD superheaters with 1/4" dia pairs of elements in each. however i have used the same arrangement and size of elements in 7/8" OD flues and in Stepney's case 3/4" OD.
do you have a view please on the subject of superheaters?
we discussed coaxial superheaters awhile back, and i know pete (greenglade) will be interested in this subject re his DONCASTER, as i think this is one big error on the DONCASTER design, and many of don young's later designs.
hope im not going off topic again!
cheers, julian
|
|
steam4ian
Elder Statesman
One good turn deserves another
Posts: 2,069
|
Post by steam4ian on Apr 14, 2015 23:19:44 GMT
Michael. The reawakening of this topic has prompted me to go back to the beginning. This in turn has led me to ponder steam locomotive development. The question then becomes; has any body/group bit by bit evaluated the form and function of each part of a steam locomotive? By this I mean as an example transmission between driving axles, are side coupling rods the best thing? What is the best way of coupling the engine or engines to the driving axles? If each engine or engine pair drove one axle how is slip managed? As an aside, various locos from SASMEE won awards at the recent AALS Easter Convention. One award winning loco is very unique being a V8 based on the German Henschel V-8 V19-1001 see www.aqpl43.dsl.pipex.com/MUSEUM/LOCOLOCO/steamotor/steamotor.htm#19The model loco runs quite successfully, a credit to Graham Driscoll the builder it but has one downfall, on uneven track a wheel set can lose adhesion and rob steam from the other engines. As for engineering Dr Allan Wallace has devised a moveable eccentric valve gear suitable for the engines and most probably similar to what Henschel used. My point, there is still room for assessment of the functional efficacy of each part of a steam locomotive even at model level. Graham Driscoll's latest effort is a turbine driven locomotive.
|
|